JET BREAK-UP CHARACTERIZATION OF MO

JET BREAK-UP CHARACTERIZATION OF
MOLYBDENUM SHAPED CHARGE LINERS
E.L. Baker*, A. Daniels, J. Pham, T. Vuong, S. DeFisher
U.S. Army, Armament Research, Development and Engineering Center
Picatinny Arsenal, NJ 07806-5000
ABSTRACT
The development of molybdenum lined shaped charges is a relatively new area of investigation, with recent emphasis placed
in producing increased jet ductility. Excellent jet ductility has now been successfully produced from a variety of molybdenum
shaped charge liners. Conventional forging and high energy rate forming (HERF) have been used to produce a variety
molybdenum shaped charge liner preforms including hemispheres, cones and trumpets. Most liner forgings exhibited good
formability using both conventional forging and HERF processing. Liner forgings have been fabricated from arc cast and
powder metallurgy molybdenum, as well as one from a single crystal. Grain size and geometry have been investigated using
scanning electron microscopy. Neutron diffraction has been used to investigate material texture through samples taken from
the base and apex regions for some of the liner forgings. Tensile tests have been used to investigate low rate material
strength and ductility. Hopkinson bar testing has been used to develop Johnson-Cook, Zerilli-Armstrong and MTS material
models. Long standoff triple flash radiography was used to evaluate overall jet ductility. All the designs produce experimental
jet tip velocities in close agreement with modeling, typically near 12.0 Km/s. Experimental trends of jet ductility were observed
with proper material selection and thermomechanical conditioning producing excellent jet ductility.
INTRODUCTION
The development of molybdenum lined shaped charges is a relatively new area of investigation. Copper has traditionally been
the liner material of choice for shaped charges. Molybdenum is an attractive material for shaped charge liners due to a high
sound speed (5.124 Km/s versus 3.94 Km/s for Cu) and a relatively high material density (10.2 g/cc versus 8.93 for Cu). The
high sound speed is desirable in order to achieve high velocity coherent jet tips [1,2]. The high material density is desirable for
penetration capability. Molybdenum has proven benefits for warhead precursor applications, where high coherent jet tip
velocities are extremely important and deep penetration capability is of lesser importance. In order for a shaped charge to
produce deep armor penetration, the stretching shaped charge jet must achieve a very long length before particulating. For
this reason, significant emphasis is placed on producing increased jet ductility [3]. The determination of desirable molybdenum
liner material properties for improved jet ductility could lead to improved performance and production processes for liner
fabrication.
DESIGN
In order to take advantage of potential molybdenum benefits, appropriate shaped charge design is vital. The differences in
material properties make the design of molybdenum shaped charges quite different than for copper lined shaped charges. The
resulting shaped charge geometries are significantly different than traditional copper lined shaped charge geometries. We
have concentrated on a number of different design types, depending on application: material investigation or warhead
application.
In order to investigate the effects of liner material properties and processing, rather than shaped charge design, a relatively
simple design that produced a robust jet with a broad velocity distribution was desired. A 73mm diameter extreme shaped
charge design with relatively simple fabrication requirements was developed using formal numerical optimization incorporated
into the analytic shaped charge model PASCC1 (Picatinny Arsenal Shaped Charge Code, 1 dimensional analysis) [4,5]. A
constant thickness conical liner with a simple truncated apex was selected for ease of fabrication. The PASCC1 numerical
optimization capability was used to determine the wave shaping axial position and diameter required to maximize the jet tip
velocity. Inequality constraints specifying a maximum allowable 1.22 collapse Mach number and a maximum allowable wave
shaper diameter of 60mm were imposed. An additional inequality constraint of no jet inverse velocity gradient was also used.
Figure 1 presents the resulting optimal design. Although the optimization result predicted a high velocity jet tip (12.5 Km/s), the



jet tip region was predicted to be extremely thin. In order to overcome this deficiency, a second optimization was performed
that maximized the smallest jet radius at 50 µs with the collapse Mach number constrained to equal 1.22. The previous
maximum allowable wave shaper diameter inequality constraint was again imposed. Figure 2 presents the resulting final
optimized design. The resulting final design was predicted to produce a robust jet with a 12.5 km/s jet tip velocity. Figure 3
presents the PASCC1 predicted jet velocity versus initial liner axial position for the two optimized designs. Figure 4 presents
the PASCC1 predicted jet radius versus jet axial position at 50µs for the two optimized designs.
Figure 1. Maximized jet tip velocity wave shaper geometry (1st Optimization).
Figure 2. Final optimized wave shaping design to produce a robust high velocity jet (2nd Optimization).
Figure 3. Jet velocity versus initial liner axial position.
Figure 4. Jet radius versus jet axial position at 50µs.


The final optimized design was computationally verified using the arbitrary Lagrange Eulerian program CALE. Figure 5
presents CALE predicted material boundaries at 0 and 32µs. The CALE calculations indicated a jet tip velocity of 11.6 Km/s.
Figure 5. Material boundaries at 0 and 32µs.
A variety of high performance shaped charge designs have been completed and experimentally tested. In particular, trumpet
shaped charge designs have been tested in a number of different design configurations. Figure 6 presents a photograph
comparing a small angle conicial molybdenum liner to a trumpet molybdenum liner. Figure 7 present three different trumpet
shaped charges that have been used in experimentation. All three designs produce similar jet tip velocities (~12. Km/s).
Detonation wave shaping is commonly used in order to prevent ultra-thin liner thicknesses which are particularly difficult to
fabricate.
Figure 6. Photograph comparing conical and trumpet molybdenum shaped charge liners.


Figure 7. Trumpet shaped charge designs.
MATERIAL PROCESSING AND JET CHARACTERIZATION
A number of different material processing methods have been used for the fabrication of molybdenum shaped charge liner
preforms including single crystal, high energy rate forming (HERF), conventional forging and hot isostatic pressing (HIP). The
emphasis of these material processing investigations has been to produce high ductility shaped charge jets, as well as to
address potential production liner manufacture methods for high performance molybdenum shaped charge warheads.
A single crystal shaped charge liner was fabricated and provided to TACOM-ARDEC by R. Sullivan of BWX Technologies,
NNFD Product Development. The monocrystal preform was machined to a ½ scale version of the conical design previously
developed for molybdenum material investigation. The orientation of the monocrystal liner was intended to be 111 oriented
along the vertical axis of liner, but analysis showed that it was about 9 degrees off axis. The warhead was loaded with Octol
70/30 and a ½ scale diameter waveshaper with full scale axial thickness was fabricated into the warhead. Long stand-off flash
radiography was used to characterize the experimental jet ductility. The resulting jet demonstrated extremely brittle behavior,
with a large amount radial particulate. Complete ductility data reduction was not completed due to the extreme jet dispersion
exhibited by the jet. Figure 8 presents a long stand-off jet x-ray result.
Figure 8. Long stand-off jet x-ray from monocrystal molybdenum lined shaped charge.
The ability to quickly tailor final liner material properties and characteristics for small numbers of liner forgings has
made high energy rate forming (HERF) an extremely valuable liner forging method for materials investigation. ARDEC has
previously used HERF for copper and tantalum warhead liner material properties investigation and processing development
[6]. Due to the success of these previous efforts, a HERF material processing investigation of molybdenum shaped charge
liners was conducted. The investigation concentrated on the effect of molybdenum liner material properties and processing on
jet ductility. Significant increases of jet ductility were achieved. High energy rate forming was used to produce liner forgings
from arc cast barstock. The near net liner preforms were made with a total of five forging blows. Although the molybdenum
liner forgings exhibited excellent formability at the high strain rates produced by the HERF process, care had to be taken to


avoid tensile cracking. A recrystallization study yielded thermal conditioning required to obtain fine grain (~12 micron)
structured recrystallized material. The liner forgings grain structures were investigated using traditional optical microscope
techniques. The unrecrystallized grains were extremely long and stringy compared to the nearly equal axis grains produced by
recrystallization. Four different thermal and mechanical conditioned liner forgings were subsequently produced using different

結果 (中文) 3:

的钼药型罩多的面包师傅，A.丹尼尔斯，J. T.范，Vuong射流断裂的表征，S. defisher
美国陆军，武器研究，发展和工程中心
皮卡汀尼兵工厂，新泽西07806-5000
摘要
钼发展内衬聚能装药是一个相对较新的研究领域，近期重点把生产增加射流延性
。优良的射流的韧性已经从各种钼
成型装药研制成功。传统的锻造、高能率成形（HERF）已用于生产各种钼药型罩坯
包括半球，锥角。大多数班轮锻件具有良好的成形性使用常规
锻造和高能率成形加工。内衬锻件已从电弧铸造和粉末冶金钼
制作，以及一个单晶体。晶粒尺寸和几何形状已使用
扫描电子显微镜研究。中子衍射研究了材料的纹理通过样本
顶端和基部的一些地区班轮锻件。拉伸试验是研究材料的强度和延性低率
。霍普金森杆试验已被用于开发约翰逊库克，Zerilli阿姆斯壮和MTS材料
模型。长时间对峙三闪光照相是用来评估整体射流延性。所有的设计制作实验
喷口速度建模接近一致，一般在12公里/秒。射流延性试验观察到的趋势，选择合适的材料和热
空调制造优良的射流延性。
介绍
钼发展内衬聚能装药是一个相对较新的研究领域。铜历来
射孔的衬里材料的选择。钼是药型罩由于高
声速的一个有吸引力的材料（5.124公里/秒和3.94公里/秒的铜）和相对高的材料的密度（10.2克/ CC和8.93铜）。
高的声音的速度以实现高速集束射流提示[1,2]是可取的。高密度材料是可取
穿透能力。钼具有弹头体的应用证明，在高相干射流头部速度非常重要
深穿透能力是不重要的。为了形成电荷
产生深刻的护甲穿透，拉伸聚能射流化之前必须达到一个很长的长度。对于
这个原因，显着的重点放在增加射流的韧性[ 3 ]。理想的内衬材料性能改进钼
射流延性确定班轮
制造导致改进的性能和生产工艺。为了设计

利用潜在的钼的好处，适当的聚能装药的设计是至关重要的。
中的差异材料的性能，使设计不同钼聚能比铜内衬聚能。
聚能装药几何的产生比传统的铜内衬聚能装药几何形状明显不同。我们
都集中在许多不同的设计类型，这取决于应用程序：材料调查或弹头

应用。为了探讨衬垫材料的性能和加工的影响，而不是聚能设计，设计简单，相对
生产具有广阔的速度分布的射流所需的强大。一个直径73mm
极端形收取设计相对简单的制造要求使用正式的数值优化纳入
发达在分析聚能模型pascc1（皮卡汀尼兵工厂聚能码，1维分析）[ 4,5 ]。一个恒定的壁厚锥形衬套
一个简单的截断顶点被选为制作方便。pascc1
优化能力的数值用于确定波形的轴向位置和直径需要最大限度地提高射流头部速度
。不等式约束指定一个最大允许崩溃1.22马赫数和最大允许波
整形器直径为60mm的实施。没有喷气反速度梯度附加不等式约束也被使用。图1给出了产生
优化设计。虽然优化结果预测高速喷射头（12.5公里/秒），第



预测是非常薄的尖端区域是射流。为了克服这一缺陷，第二进行优化，最大化最小
喷射半径在50的崩溃µ马赫数约束等于1.22。以前允许的最大波整形器直径
不等式约束又强加。图2给出了最终
优化设计。预计生产12.5公里/秒的射流头部速度一个强大的射流产生的最终设计。图3给出了射流速度
pascc1预测与初始线性轴向位置的优化设计。图4给出了预测的射流半径与
pascc1射流轴向位置在50的两µ
图1优化设计。最大射流头部速度波形整形几何（第一优化）
图2。最终优化的波形设计来产生一个强大的高速射流（第二优化）
图3。射流速度与初始线性轴向位置
图4。射流与射流轴向位置50µ


S.最终的优化设计计算验证，采用任意拉格朗日-欧拉程序规模。图5给出了凯尔
预测材料的界限在0和32秒。凯尔µ计算表明11.6公里/秒
图5射流头部速度。在0和32材料边界µS.
各种高性能聚能装药的设计已经完成，实验测试。特别是，小号
聚能设计已在许多不同的设计配置测试。图6给出了一个比较小的角度拍摄
conicial钼衬角钼衬里。图7给出了三个不同的小号
形已被用于实验的费用。三设计生产类似的射流头部速度（~ 12。
公里/秒）。爆轰波整形常用为了防止超薄衬垫厚度是特别难

制作。图6。相比圆锥喇叭钼药型罩


图7。喇叭形的电荷设计。
材料加工和射流特性
许多不同的材料处理方法已用于钼药型罩
预制件包括单晶的制备，高能率成形（HERF），常规锻造和热等静压（HIP）。这些材料加工研究的重点一直是
生产高延性聚能射流，以及
解决潜在的生产线制造方法的高性能钼聚能装药弹头。
制作和R.沙利文的BWX技术TACOM-ARDEC提供了一种单晶聚能罩，
nnfd产品开发。单晶毛坯加工成的锥形设计½规模以前
开发的钼材料的研究。的单晶衬定位的目的是面向111沿垂直轴
衬垫，但分析表明，它是约9度的离轴。战斗部装有70 / 30和Octol
½规模直径波形满刻度的轴向厚度制成的弹头。长时间的对峙闪光
摄影被用来表征延性试验飞机。由此产生的射流表现出极为脆性行为，
大量径向颗粒。完整的延展性数据的减少是由于极端的射流的射流具有完成
。图8显示了长时间的对峙喷射的X射线结果
图8。长时间的对峙喷射X射线单晶衬钼聚能
。很快的小数量的线性锻件裁缝最终衬垫材料的性质和特征的能力
了高能率成形（HERF）极其珍贵的锻造材料衬里的调查方法。美国陆军已
铜和钽的弹头内衬材料性能的调查与处理发展
[ 6 ]以前使用的高能率成形。由于这些努力的成功，一个高能材料加工研究钼聚能
衬垫进行。调查集中在钼衬里材料性能和加工对
射流延性的影响。实现了射流的韧性显著增加。高能率成形用于铸造棒材锻件生产班轮
弧。近净衬垫预制块总共五锻造击打。虽然钼衬具有良好的成形锻件
的高能率成形过程产生的高应变率，护理必须采取


避免开裂。研究了再结晶热空调需要获得细晶粒（~ 12微米）
结构再结晶材料。使用传统的光学显微镜技术研究了班轮
锻件晶粒结构。比较由
再结晶产生的近等轴晶粒的再结晶晶粒非常的长而细的。四种不同的热机械条件班轮锻件随后使用不同的